A Biacore Model 3000 is requested in this Shared Instrument Grant application. The instrument will allow a group of 6 N.I.H.-funded investigators to complete their studies of macromolecular interactions. Four of the six investigators currently have N.I.H. grants where surface plasmon resonance (SPR) experiments are specified. Recent increases in the use of the only SPR instrument, a Biacore 2000 located in the Ohio State Comprehensive Cancer Center, has reduced available instrument time to such an extent that timely completion of this work is threatened. A Biacore 3000 represents the best purchase option for this group of investigators based on ongoing, proposed and extension of the SPR-based investigations. The instrument will be housed in the Flow Cytometry Service Laboratory under the supervision of a State-paid Research Scientist with experience in the operation and maintenance of optical-flow instruments. The supervisor will receive initial training from Biacore and will be provided further training opportunities as instrument applications expand. Users will be certified by attending a training secession given by the laboratory supervisor. Access to a Web-based scheduler will be given only to individuals who have successfully completed training. In order to maximize instrument availability, users will be provided with 24 hour/day keyed access. The instrument will be run in a Windows NT environment, which will allow users to check the progress of on-going experiments from distant sites. An hourly user fee will provide funds for a service contract and continuing education for the supervisor. Billing will be performed through the current system of the Flow Cytometry Lab with revenues kept in a separate account. Space and utilities for the instrument plus salary and benefits for the supervisor will be provided by the Department of Veterinary Biosciences and the College of Veterinary Medicine.